I. Field of the Invention
The present invention pertains to a method and apparatus for surface finishing a manufactured article and, more particularly, a system for providing a substantially constant polishing force during the finishing process.
II. Description of the Prior Art
After an article is manufactured, it is often necessary to finish the outer surface of the article. For instance, if the article is die casted, burrs are often formed on the article's outer surface. In addition, it is not uncommon for fine cracks to develop in a casting die due to thermal fatigue which can result in surface undulations in the casted product which must be removed. Surface finishing is often required for both metal products and plastic moldings.
Although such finishing operations are generally manually performed, it is desirable to automate the process. In this connection, an industrial robot may be utilized which includes an arm for grasping the work article and bringing it into contact with the polishing tool. (As used herein, "polishing" is a generic term for surface finishing and can include such finishing operations as grinding and sanding.) The industrial robot can be programmed to transfer the work product to specified locations so as to come into contact with a polishing tool and to reposition the work product so that multiple surfaces thereof can be finished. In practice, it has been found that the contact pressure between the finishing tool and successive work products vary due to wearing of the polishing tool.
To compensate for varying contact pressures, it is possible to alter the program of the industrial robot such that the work product is repositioned on the basis of detected wear of the polishing tool. Unfortunately, such arrangements require complicated and expensive system changes. For instance, not only is a sensor for detecting the wear of the polishing tool required, a special function must also be added to the robot to vary its range of movement.
In addition, if the polishing tool wears unevenly, it becomes necessary to reshape the polishing tool which results in down time of the finishing system. Further, if the work product is excessively forced against the polishing tool, the robot motor could be damaged. Therefore, in such a system, the robot must be provided with a protection system which further complicates the operation of the robot and adds to its expense.
Therefore, there exists a need in the art for a method and apparatus for finishing a work product which can compensate for polishing tool wear which will not require additional programming or an overload protection system to be added to the robot controls. In general, there exists a need to provide a simple assembly for compensating for wear on a polishing tool so that a consistent surface finish can be provided on successive manufactured products.